I agree with you, the police do seem to be applying pressure to encourage a confession.
This is an old trick with the police, although they do not appear to have a clue they apply pressure just to break people and get a confession.
It matters not that they may be innocent, that they have lost their child; just get a confession come what may to close the book on it.
No one can know the truth not the perverse, the cynical or anyone else until the case is investigated in an intelligent and proper fashion.